
\section {Discussion} \label{discussion}
%\emph{
% lexeme acquisition rate, supports our hypothesis \\
% Taxonomical vs. Absolute improvement, explanations, (add "primacy of nouns" explanation)  \\
% Error overcoming, Success rate explanations \\
% Example, speed and inference \\
% visibility of objects, visual saliency ; Explanation, why visibility is not applicable in our case  \\ 
% subjective metrics : object identification evaluation\\
% exercise room utility evaluation \\}

	Our initial hypothesis was that overspecification improves the lexeme acquisition rate. According to this hypothesis, the subjects who received overspecified references should acquire vocabulary more efficiently than those who received minimal ones. This was confirmed by our results: the overall OR lexeme acquisition rate was significantly higher than the rate of the MR condition.

	For Taxonomical and Absolute lexeme acquisition rates, we can observe that OR results were almost twice higher than MR ones. In the case of Taxonomical lexemes, the OR acquisition rate was 100\%, compared to the MR acquisition rate of only 53\%. In the case of Absolute lexemes, the acquisition rate in the OR condition was slightly lower (87.5\% for OR and 45\% for MR), which can be explained by the Primacy of Nouns \cite{genter82}, which postulates that the acquisition of new nouns is easier because the category corresponding to nouns is conceptually simpler than those of verbs or adjectives. 

	Other objective metrics that we consider are error overcoming and success rates, which are both higher for the OR condition. By the Second Test Phrase the number of errors committed by the OR subjects dropped with a 43\% error overcoming rate, compared to only 29\% for MR subjects (See Table 2). Also, the Exercise Phase success rate for OR was 8.7\%  higher, meaning that, in average, people were better at identifying objects when overspecification was provided (See Table 3). This is a corroboration of the higher utility of the Exercise Phase with the OR condition. 
%There are different possible explanations for this: for instance, that OR subjects had the possibility of inferring lexemes during the Exercise Phase, or simply that they had more exposition to the new lexemes. 
%\fxnote{SV: unneeded phrase? }  

	So far we have measured that in the experiment, if the RE given was the Russian equivalent of  ``yellow chair", the MR subject had no way of inferring which object was being referred to if they did not know \emph{both} the Absolute property ``yellow" \emph{and} the Taxonomical property ``chair". However, if the RE given was ``yellow chair on the left of the red light", even if the subject did not remember the first two words, they could use the rest of the RE to \emph{infer} the object in question. Possible proof of this inference process is that it took OR subjects twice as long to resolve the REs (See Table 3). We believe that if the subjects were able to infer the referent of the RE and received the positive feedback after its identification, they could then make the connection between the previously missing properties and the properties of the object chosen, and thereby acquire new lexemes and improve their performance in the Second Test Phase.

	A final objective parameter that we examined in our analysis was whether or not the visibility of the object referred to affected the resolution of the reference. In general, visual saliency plays a key role in the resolution of REs \cite{Kelleher_2008,Kelleher_Costello_Vangenabith_2005}.  From the 178 references given when the object was in the subject’s field of vision, only 105 were successfully resolved, which is a 59\% success rate, lower than the average Exercise Phase success rate for the two groups. This means that the situatedness of the subject within the virtual world did not have such an effect on the success rate as expected. The reason for this might be that, in the context of our experiment, each subsequent reference was given when the button corresponding to the previous one was pushed and not a general view of the room. A truly indicative proof of visual saliency would therefore have to be further tested in a different experiment, for instance one in which the subject receives a reference while looking at more objects in the room.

	For subjective metrics, there are two questions in particular that are of interest to our results: whether the subjects thought that the descriptions given in Russian were appropriate, and to what extent they thought that the Exercise Room helped them remember the words learned (Q3 and Q4 in Table 4). For Q3, we found no statistically significant difference between the OR and MR conditions. That is, even though OR descriptions may be considered more ``cognitively demanding", they were not judged more difficult to understand by the subjects. Evidence that OR descriptions may be more cognitively demanding is that the resolution speed was twice as slow for OR subjects and overspecified REs included more vocabulary for subjects to process. This is also consistent with the results of Engelhardt's experiments \shortcite{Engelhardt_Bailey_Ferreira_2006} in which it was found that listeners ``do not judge over-descriptions to be any worse than concise expressions". 

	We found that the subject's evaluations of the utility of the Exercise Room to be significantly higher in the OR condition, which shows that the participants themselves deemed that the overspecification training exercises were more useful to them than the minimal specification exercises. Subjects from the OR condition rated the Exercise Room as being  more effective than the subjects from the MR condition (75\% compared to 86\%). Subjects perceived the training exercises as more effective when overspecified REs were used, as opposed to minimal specification REs. This is a further corroboration of our hypothesis regarding the utility of overspecification, this time in subjective terms. 
